I have 2 fields on my form abtnm & abtnmR, for both the default value is "". Field abtnm's value (text) is chosen, by the user, via a dialog list that uses a @DbColumn fucntion for choices. Field abtnmR's value can also be chosen via a dialog list that uses a @DBlookup function based on the value of abtnm for choices, OR it can be left blank.
I want the value of abtnmR to default to the value of abtnm if the field is left blank.
How can I do this?